1. Field of the Invention
This invention relates to the detergent industry.
2. Description of the Art Practices
Sulfated organic surfactants have been known for many years, the first having been prepared by Dumas in 1836. When organic sulfate surfactants are manufactured a difficulty exists in obtaining a high active content product. In some applications this is unimportant as the inactive portion of the composition will either be water and/or inorganic salts. The water is present as a product from the neutralization reaction and from use as a solvent, i.e. aqueous caustic. If one is directly manufacturing a detergent product for use as a household dishwashing composition then the amount of water in the formulation is somewhat immaterial as these products contain a high portion of water. Similarly the presence of inorganic salts are of no great consequence when the end product is a solid as the inorganic sulfate salt aids in forming crisp granules.
It is however highly desirable to obtain high active content organic sulfate products when the surfactants are manufactured for sale to customers who desire to have an anhydrous product to lower shipping costs or to those who wish to obtain a high active formulation. Similarly oil field applications of such materials where foaming is desired only at the well site and not prior to placing the surfactant in the well require specialized products with which the present invention is concerned.
There have been attempts in the art to manufacture what are essentially anhydrous surfactant products. For instance it is possible to obtain alkyl sulfates or alkyl ether sulfates at up to 30 percent solids in water without encountering any great difficulty. In current practice an alcohol or alcohol ethoxylate are reacted with a sulfating agent to form a sauer ester and thereafter the sauer ester is neutralized with aqueous caustic to give the sodium salt. By sauer ester it is meant that the alcohol, ethoxylated alcohol, olefin, or alkylbenzene which can be converted to a sulfate (sulfonate) salt is first reacted with a sulfating agent to give the sauer ester which is in fact an acid ester.
This technology allows the alkyl ether sulfate or alkyl sulfate to be obtained in concentrations of 20 to 40 percent by weight in water. A particular difficulty with this technology is however that the sauer ester must be mixed extremely thoroughly and rapidly with the caustic to avoid hydrolysis of the sauer ester back to the starting unsulfated material. Where this hydrolysis occurs the product will contain for example the starting alcohol, and as the hydrolysis also generates sulfuric acid, sodium sulfate will also be formed. As this reaction invariably takes place to some extent the active content is lost and a fatty alcohol is generated in the product which is of little use, if not a detriment to the product. Moreover the sodium sulfate formed in the reaction mixture complicates further processing and adds nothing to the product when a high active concentration is desired.
In order to alleviate the problems described above it has been suggested that products with a 60 percent active concentration of an alkyl sulfate or alkyl ether sulfate may be formulated.
However to allow processing of such products it has been found necessary to utilize substantial amounts of solubilizing agents such as glycols or lower monohydric alcohols. This is despite the fact that the product is already dissolved in 40% water. These hydrotropes aid in maintaining the product in a semi-fluid state but also have an effect on the ability of the product to remain clear when in a liquid state.
As previously noted the caustic neutralization step will result in a small amount of the starting alcohol and sodium sulfate in the product. Moreover, the processing also inherently leaves substantial amounts of water which again are not desired in some applications.
Even with this aforedescribed technology the high active content is particularly subject to the hydrolysis previously discussed, and it is necessary to vigorously mix the product. It is further known that it is possible to obtain alkyl sulfates and alkyl ether sulfates with concentrations as high as 70 percent by weight solids with the remainder being substantially aqueous if proper mixing techniques are used in the neutralization step.
Unfortunately the mixing system for such a product still allows some hydrolysis to occur thereby generating the starting alcohol and the inorganic sulfate salt. Moreover, when a 70 percent active concentration is obtained the product has the consistency of vaseline and during the processing the viscosity may reach 2 million cps. It has also been noted that when such products are sold that the end user of the formulation when diluting out the vaseline type product with water will again encounter the 2 million cps viscosity thus limiting the use of such products to a low feed rate into a reaction or alternatively presents the need for substantial investment in mixing equipment.
It has been suggested in U.S. Pat. No. 3,728,265 issued Apr. 17, 1973 to Chella et al, that high foaming liquid detergent compositions may be formulated for use in non-pressurized containers wherein the product contains a compressible water-insoluble gas, an organic solvent such as propylene glycol, a water-soluble anionic detergent, and an alkanolamide. U.S. Pat. No. 3,850,831 to Hellsten et al describes liquid detergent compositions containing a surfactant, a peroxide bleaching agent and a polyhydric alcohol in a substantially anhydrous formulation.
It is described in Canadian Pat. No. 1,028,957 to Mackles to form a detergent product which is a combination of a propellant, and a material which is a coconut oil diethanolamide neutralized with lauryl ether sulfate and further containing isostearic acid diethanolamide.
Therefore there remains, and the present invention deals with the obtaining of high active content formulations of an alkyl ether sulfate, alkyl benzene sulfonate, olefin sulfonate or alkyl sulfate containing only minimal amounts of inorganic salts and minimal amounts of the starting alcohol. Such products are also desirably to be liquids of low viscosity and high clarity with limited water content. Products of the present invention are useful for any of the purposes that such surfactants are used including personal care products, household, institutional and industrial detergents; including such uses as shampoos, bubble baths, hand soaps, emulsions, emulsion polymerization, oil field chemicals, hard surface cleaners, laundry and dishwashing detergents, paper processing, gypsum board formers and other uses.
Throughout the specification and claims percentages and ratios are by weight, pressures are gauge and temperatures are Celsius unless otherwise indicated. The terms alkyl ether sulfate, alkyl alkoxy sulfate, alcohol ether sulfate and the like are used interchangably. The term organic anionic sulfate embraces the former materials as well as alkyl sulfate. For practical purposes the term sulfating agent also is used when referring to a sulfonating agent. Olefin sulfonate is used herein, however, it is recognized that the unsaturation is lost in the sulfation reaction giving an alpha-substituted sulfonate.